HT 903 DVD player - surround sound service manual.

[Pommie]

A friend of mine asked me to look at her surround sound system. It powers up and then a few seconds later displays Goodbye and powers down. The display is very dim so I suspect one of the power rails is out of spec. Inside there's a single sided power supply board and a heavily populated multi sided amp/dvd player board. The amp board is labelled HT503 HT903 so I suspect the 903 designation is a South African code as that was where it was purchased.

Anyone got any information on this device, especially the power board.

Thanks,

Mike.

 

[Nigel Goodwin]

What make is it?.

If you suspect PSU, I would run the scope round the supply rails (on the outputs of the rectifiers), to check for ripple caused by high ESR electrolytics.

The dim display 'may' be a red herring though, as (assuming it's a CCFL display) they tend to have a fairly short lifespan, and rapidly become too dull to see.

Very, very, occasionally you do find a duff PSU capacitor causing it though - I've changed dozens of high ESR capacitors for dim displays, and only improved things in a couple of cases (and not great then, but better than it was).

It 'could' be shutting down due to an output protection fault, due to a duff output IC, or (more commonly in surround systems) dry joints on the IC's or surrounding components.

 

[Pommie]

Thanks Nigel, it's an LG made in 2009. Guess it's time to dig out my scope.

Mike.